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  <div class="headertitle"><div class="title">Choosing memory type</div></div>
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<div class="textblock"><p>Physical devices in Vulkan support various combinations of memory heaps and types. Help with choosing correct and optimal memory type for your specific resource is one of the key features of this library. You can use it by filling appropriate members of <a class="el" href="struct_vma_allocation_create_info.html" title="Parameters of new VmaAllocation.">VmaAllocationCreateInfo</a> structure, as described below. You can also combine multiple methods.</p>
<ol type="1">
<li>If you just want to find memory type index that meets your requirements, you can use function: <a class="el" href="group__group__alloc.html#gae790ab9ffaf7667fb8f62523e6897888" title="Helps to find memoryTypeIndex, given VkBufferCreateInfo and VmaAllocationCreateInfo.">vmaFindMemoryTypeIndexForBufferInfo()</a>, <a class="el" href="group__group__alloc.html#ga088da83d8eaf3ce9056d9ea0b981d472" title="Helps to find memoryTypeIndex, given VkImageCreateInfo and VmaAllocationCreateInfo.">vmaFindMemoryTypeIndexForImageInfo()</a>, <a class="el" href="group__group__alloc.html#gaef15a94b58fbcb0fe706d5720e84a74a" title="Helps to find memoryTypeIndex, given memoryTypeBits and VmaAllocationCreateInfo.">vmaFindMemoryTypeIndex()</a>.</li>
<li>If you want to allocate a region of device memory without association with any specific image or buffer, you can use function <a class="el" href="group__group__alloc.html#gabf28077dbf82d0908b8acbe8ee8dd9b8" title="General purpose memory allocation.">vmaAllocateMemory()</a>. Usage of this function is not recommended and usually not needed. <a class="el" href="group__group__alloc.html#gad37e82e492b3de38fc3f4cffd9ad0ae1" title="General purpose memory allocation for multiple allocation objects at once.">vmaAllocateMemoryPages()</a> function is also provided for creating multiple allocations at once, which may be useful for sparse binding.</li>
<li>If you already have a buffer or an image created, you want to allocate memory for it and then you will bind it yourself, you can use function <a class="el" href="group__group__alloc.html#ga7fdf64415b6c3d83c454f28d2c53df7b" title="Allocates memory suitable for given VkBuffer.">vmaAllocateMemoryForBuffer()</a>, <a class="el" href="group__group__alloc.html#ga0faa3f9e5fb233d29d1e00390650febb" title="Allocates memory suitable for given VkImage.">vmaAllocateMemoryForImage()</a>. For binding you should use functions: <a class="el" href="group__group__alloc.html#ga6b0929b914b60cf2d45cac4bf3547470" title="Binds buffer to allocation.">vmaBindBufferMemory()</a>, <a class="el" href="group__group__alloc.html#ga3d3ca45799923aa5d138e9e5f9eb2da5" title="Binds image to allocation.">vmaBindImageMemory()</a> or their extended versions: <a class="el" href="group__group__alloc.html#ga861f4f27189a7d11ab9d9eedc825cb6b" title="Binds buffer to allocation with additional parameters.">vmaBindBufferMemory2()</a>, <a class="el" href="group__group__alloc.html#ga5f3502dd7d38b53fb1533ea3921d038d" title="Binds image to allocation with additional parameters.">vmaBindImageMemory2()</a>.</li>
<li>If you want to create a buffer or an image, allocate memory for it, and bind them together, all in one call, you can use function <a class="el" href="group__group__alloc.html#gac72ee55598617e8eecca384e746bab51" title="Creates a new VkBuffer, allocates and binds memory for it.">vmaCreateBuffer()</a>, <a class="el" href="group__group__alloc.html#ga02a94f25679275851a53e82eacbcfc73" title="Function similar to vmaCreateBuffer().">vmaCreateImage()</a>. <b>This is the easiest and recommended way to use this library!</b></li>
</ol>
<p>When using 3. or 4., the library internally queries Vulkan for memory types supported for that buffer or image (function <code>vkGetBufferMemoryRequirements()</code>) and uses only one of these types.</p>
<p>If no memory type can be found that meets all the requirements, these functions return <code>VK_ERROR_FEATURE_NOT_PRESENT</code>.</p>
<p>You can leave <a class="el" href="struct_vma_allocation_create_info.html" title="Parameters of new VmaAllocation.">VmaAllocationCreateInfo</a> structure completely filled with zeros. It means no requirements are specified for memory type. It is valid, although not very useful.</p>
<h1><a class="anchor" id="choosing_memory_type_usage"></a>
Usage</h1>
<p>The easiest way to specify memory requirements is to fill member <a class="el" href="struct_vma_allocation_create_info.html#accb8b06b1f677d858cb9af20705fa910" title="Intended usage of memory.">VmaAllocationCreateInfo::usage</a> using one of the values of enum <a class="el" href="group__group__alloc.html#gaa5846affa1e9da3800e3e78fae2305cc" title="Intended usage of the allocated memory.">VmaMemoryUsage</a>. It defines high level, common usage types. Since version 3 of the library, it is recommended to use <a class="el" href="group__group__alloc.html#ggaa5846affa1e9da3800e3e78fae2305cca27cde9026a84d34d525777baa41fce6e">VMA_MEMORY_USAGE_AUTO</a> to let it select best memory type for your resource automatically.</p>
<p>For example, if you want to create a uniform buffer that will be filled using transfer only once or infrequently and then used for rendering every frame as a uniform buffer, you can do it using following code. The buffer will most likely end up in a memory type with <code>VK_MEMORY_PROPERTY_DEVICE_LOCAL_BIT</code> to be fast to access by the GPU device.</p>
<div class="fragment"><div class="line">VkBufferCreateInfo bufferInfo = { VK_STRUCTURE_TYPE_BUFFER_CREATE_INFO };</div>
<div class="line">bufferInfo.size = 65536;</div>
<div class="line">bufferInfo.usage = VK_BUFFER_USAGE_UNIFORM_BUFFER_BIT | VK_BUFFER_USAGE_TRANSFER_DST_BIT;</div>
<div class="line"> </div>
<div class="line"><a class="code hl_struct" href="struct_vma_allocation_create_info.html">VmaAllocationCreateInfo</a> allocInfo = {};</div>
<div class="line">allocInfo.<a class="code hl_variable" href="struct_vma_allocation_create_info.html#accb8b06b1f677d858cb9af20705fa910">usage</a> = <a class="code hl_enumvalue" href="group__group__alloc.html#ggaa5846affa1e9da3800e3e78fae2305cca27cde9026a84d34d525777baa41fce6e">VMA_MEMORY_USAGE_AUTO</a>;</div>
<div class="line"> </div>
<div class="line">VkBuffer buffer;</div>
<div class="line"><a class="code hl_struct" href="struct_vma_allocation.html">VmaAllocation</a> allocation;</div>
<div class="line"><a class="code hl_function" href="group__group__alloc.html#gac72ee55598617e8eecca384e746bab51">vmaCreateBuffer</a>(allocator, &amp;bufferInfo, &amp;allocInfo, &amp;buffer, &amp;allocation, <span class="keyword">nullptr</span>);</div>
<div class="ttc" id="agroup__group__alloc_html_gac72ee55598617e8eecca384e746bab51"><div class="ttname"><a href="group__group__alloc.html#gac72ee55598617e8eecca384e746bab51">vmaCreateBuffer</a></div><div class="ttdeci">VkResult vmaCreateBuffer(VmaAllocator allocator, const VkBufferCreateInfo *pBufferCreateInfo, const VmaAllocationCreateInfo *pAllocationCreateInfo, VkBuffer *pBuffer, VmaAllocation *pAllocation, VmaAllocationInfo *pAllocationInfo)</div><div class="ttdoc">Creates a new VkBuffer, allocates and binds memory for it.</div></div>
<div class="ttc" id="agroup__group__alloc_html_ggaa5846affa1e9da3800e3e78fae2305cca27cde9026a84d34d525777baa41fce6e"><div class="ttname"><a href="group__group__alloc.html#ggaa5846affa1e9da3800e3e78fae2305cca27cde9026a84d34d525777baa41fce6e">VMA_MEMORY_USAGE_AUTO</a></div><div class="ttdeci">@ VMA_MEMORY_USAGE_AUTO</div><div class="ttdef"><b>Definition</b> vk_mem_alloc.h:527</div></div>
<div class="ttc" id="astruct_vma_allocation_create_info_html"><div class="ttname"><a href="struct_vma_allocation_create_info.html">VmaAllocationCreateInfo</a></div><div class="ttdoc">Parameters of new VmaAllocation.</div><div class="ttdef"><b>Definition</b> vk_mem_alloc.h:1263</div></div>
<div class="ttc" id="astruct_vma_allocation_create_info_html_accb8b06b1f677d858cb9af20705fa910"><div class="ttname"><a href="struct_vma_allocation_create_info.html#accb8b06b1f677d858cb9af20705fa910">VmaAllocationCreateInfo::usage</a></div><div class="ttdeci">VmaMemoryUsage usage</div><div class="ttdoc">Intended usage of memory.</div><div class="ttdef"><b>Definition</b> vk_mem_alloc.h:1271</div></div>
<div class="ttc" id="astruct_vma_allocation_html"><div class="ttname"><a href="struct_vma_allocation.html">VmaAllocation</a></div><div class="ttdoc">Represents single memory allocation.</div></div>
</div><!-- fragment --><p>If you have a preference for putting the resource in GPU (device) memory or CPU (host) memory on systems with discrete graphics card that have the memories separate, you can use <a class="el" href="group__group__alloc.html#ggaa5846affa1e9da3800e3e78fae2305ccae2adb696d6a73c18bb20c23666661327">VMA_MEMORY_USAGE_AUTO_PREFER_DEVICE</a> or <a class="el" href="group__group__alloc.html#ggaa5846affa1e9da3800e3e78fae2305cca9b422585242160b8ed3418310ee6664d">VMA_MEMORY_USAGE_AUTO_PREFER_HOST</a>.</p>
<p>When using <code>VMA_MEMORY_USAGE_AUTO*</code> while you want to map the allocated memory, you also need to specify one of the host access flags: <a class="el" href="group__group__alloc.html#ggad9889c10c798b040d59c92f257cae597a9be224df3bfc1cfa06203aed689a30c5">VMA_ALLOCATION_CREATE_HOST_ACCESS_SEQUENTIAL_WRITE_BIT</a> or <a class="el" href="group__group__alloc.html#ggad9889c10c798b040d59c92f257cae597add61238d98e20917b9a06c617763f492">VMA_ALLOCATION_CREATE_HOST_ACCESS_RANDOM_BIT</a>. This will help the library decide about preferred memory type to ensure it has <code>VK_MEMORY_PROPERTY_HOST_VISIBLE_BIT</code> so you can map it.</p>
<p>For example, a staging buffer that will be filled via mapped pointer and then used as a source of transfer to the buffer described previously can be created like this. It will likely end up in a memory type that is <code>HOST_VISIBLE</code> and <code>HOST_COHERENT</code> but not <code>HOST_CACHED</code> (meaning uncached, write-combined) and not <code>DEVICE_LOCAL</code> (meaning system RAM).</p>
<div class="fragment"><div class="line">VkBufferCreateInfo stagingBufferInfo = { VK_STRUCTURE_TYPE_BUFFER_CREATE_INFO };</div>
<div class="line">stagingBufferInfo.size = 65536;</div>
<div class="line">stagingBufferInfo.usage = VK_BUFFER_USAGE_TRANSFER_SRC_BIT;</div>
<div class="line"> </div>
<div class="line"><a class="code hl_struct" href="struct_vma_allocation_create_info.html">VmaAllocationCreateInfo</a> stagingAllocInfo = {};</div>
<div class="line">stagingAllocInfo.<a class="code hl_variable" href="struct_vma_allocation_create_info.html#accb8b06b1f677d858cb9af20705fa910">usage</a> = <a class="code hl_enumvalue" href="group__group__alloc.html#ggaa5846affa1e9da3800e3e78fae2305cca27cde9026a84d34d525777baa41fce6e">VMA_MEMORY_USAGE_AUTO</a>;</div>
<div class="line">stagingAllocInfo.<a class="code hl_variable" href="struct_vma_allocation_create_info.html#add09658ac14fe290ace25470ddd6d41b">flags</a> = <a class="code hl_enumvalue" href="group__group__alloc.html#ggad9889c10c798b040d59c92f257cae597a9be224df3bfc1cfa06203aed689a30c5">VMA_ALLOCATION_CREATE_HOST_ACCESS_SEQUENTIAL_WRITE_BIT</a>;</div>
<div class="line"> </div>
<div class="line">VkBuffer stagingBuffer;</div>
<div class="line"><a class="code hl_struct" href="struct_vma_allocation.html">VmaAllocation</a> stagingAllocation;</div>
<div class="line"><a class="code hl_function" href="group__group__alloc.html#gac72ee55598617e8eecca384e746bab51">vmaCreateBuffer</a>(allocator, &amp;stagingBufferInfo, &amp;stagingAllocInfo, &amp;stagingBuffer, &amp;stagingAllocation, <span class="keyword">nullptr</span>);</div>
<div class="ttc" id="agroup__group__alloc_html_ggad9889c10c798b040d59c92f257cae597a9be224df3bfc1cfa06203aed689a30c5"><div class="ttname"><a href="group__group__alloc.html#ggad9889c10c798b040d59c92f257cae597a9be224df3bfc1cfa06203aed689a30c5">VMA_ALLOCATION_CREATE_HOST_ACCESS_SEQUENTIAL_WRITE_BIT</a></div><div class="ttdeci">@ VMA_ALLOCATION_CREATE_HOST_ACCESS_SEQUENTIAL_WRITE_BIT</div><div class="ttdef"><b>Definition</b> vk_mem_alloc.h:636</div></div>
<div class="ttc" id="astruct_vma_allocation_create_info_html_add09658ac14fe290ace25470ddd6d41b"><div class="ttname"><a href="struct_vma_allocation_create_info.html#add09658ac14fe290ace25470ddd6d41b">VmaAllocationCreateInfo::flags</a></div><div class="ttdeci">VmaAllocationCreateFlags flags</div><div class="ttdoc">Use VmaAllocationCreateFlagBits enum.</div><div class="ttdef"><b>Definition</b> vk_mem_alloc.h:1265</div></div>
</div><!-- fragment --><p>For more examples of creating different kinds of resources, see chapter <a class="el" href="usage_patterns.html">Recommended usage patterns</a>. See also: <a class="el" href="memory_mapping.html">Memory mapping</a>.</p>
<p>Usage values <code>VMA_MEMORY_USAGE_AUTO*</code> are legal to use only when the library knows about the resource being created by having <code>VkBufferCreateInfo</code> / <code>VkImageCreateInfo</code> passed, so they work with functions like: <a class="el" href="group__group__alloc.html#gac72ee55598617e8eecca384e746bab51" title="Creates a new VkBuffer, allocates and binds memory for it.">vmaCreateBuffer()</a>, <a class="el" href="group__group__alloc.html#ga02a94f25679275851a53e82eacbcfc73" title="Function similar to vmaCreateBuffer().">vmaCreateImage()</a>, <a class="el" href="group__group__alloc.html#gae790ab9ffaf7667fb8f62523e6897888" title="Helps to find memoryTypeIndex, given VkBufferCreateInfo and VmaAllocationCreateInfo.">vmaFindMemoryTypeIndexForBufferInfo()</a> etc. If you allocate raw memory using function <a class="el" href="group__group__alloc.html#gabf28077dbf82d0908b8acbe8ee8dd9b8" title="General purpose memory allocation.">vmaAllocateMemory()</a>, you have to use other means of selecting memory type, as described below.</p>
<dl class="section note"><dt>Note</dt><dd>Old usage values (<code>VMA_MEMORY_USAGE_GPU_ONLY</code>, <code>VMA_MEMORY_USAGE_CPU_ONLY</code>, <code>VMA_MEMORY_USAGE_CPU_TO_GPU</code>, <code>VMA_MEMORY_USAGE_GPU_TO_CPU</code>, <code>VMA_MEMORY_USAGE_CPU_COPY</code>) are still available and work same way as in previous versions of the library for backward compatibility, but they are deprecated.</dd></dl>
<h1><a class="anchor" id="choosing_memory_type_required_preferred_flags"></a>
Required and preferred flags</h1>
<p>You can specify more detailed requirements by filling members <a class="el" href="struct_vma_allocation_create_info.html#a9166390303ff42d783305bc31c2b6b90" title="Flags that must be set in a Memory Type chosen for an allocation.">VmaAllocationCreateInfo::requiredFlags</a> and <a class="el" href="struct_vma_allocation_create_info.html#a7fe8d81a1ad10b2a2faacacee5b15d6d" title="Flags that preferably should be set in a memory type chosen for an allocation.">VmaAllocationCreateInfo::preferredFlags</a> with a combination of bits from enum <code>VkMemoryPropertyFlags</code>. For example, if you want to create a buffer that will be persistently mapped on host (so it must be <code>HOST_VISIBLE</code>) and preferably will also be <code>HOST_COHERENT</code> and <code>HOST_CACHED</code>, use following code:</p>
<div class="fragment"><div class="line"><a class="code hl_struct" href="struct_vma_allocation_create_info.html">VmaAllocationCreateInfo</a> allocInfo = {};</div>
<div class="line">allocInfo.<a class="code hl_variable" href="struct_vma_allocation_create_info.html#a9166390303ff42d783305bc31c2b6b90">requiredFlags</a> = VK_MEMORY_PROPERTY_HOST_VISIBLE_BIT;</div>
<div class="line">allocInfo.<a class="code hl_variable" href="struct_vma_allocation_create_info.html#a7fe8d81a1ad10b2a2faacacee5b15d6d">preferredFlags</a> = VK_MEMORY_PROPERTY_HOST_COHERENT_BIT | VK_MEMORY_PROPERTY_HOST_CACHED_BIT;</div>
<div class="line">allocInfo.<a class="code hl_variable" href="struct_vma_allocation_create_info.html#add09658ac14fe290ace25470ddd6d41b">flags</a> = <a class="code hl_enumvalue" href="group__group__alloc.html#ggad9889c10c798b040d59c92f257cae597add61238d98e20917b9a06c617763f492">VMA_ALLOCATION_CREATE_HOST_ACCESS_RANDOM_BIT</a> | <a class="code hl_enumvalue" href="group__group__alloc.html#ggad9889c10c798b040d59c92f257cae597a11da372cc3a82931c5e5d6146cd9dd1f">VMA_ALLOCATION_CREATE_MAPPED_BIT</a>;</div>
<div class="line"> </div>
<div class="line">VkBuffer buffer;</div>
<div class="line"><a class="code hl_struct" href="struct_vma_allocation.html">VmaAllocation</a> allocation;</div>
<div class="line"><a class="code hl_function" href="group__group__alloc.html#gac72ee55598617e8eecca384e746bab51">vmaCreateBuffer</a>(allocator, &amp;bufferInfo, &amp;allocInfo, &amp;buffer, &amp;allocation, <span class="keyword">nullptr</span>);</div>
<div class="ttc" id="agroup__group__alloc_html_ggad9889c10c798b040d59c92f257cae597a11da372cc3a82931c5e5d6146cd9dd1f"><div class="ttname"><a href="group__group__alloc.html#ggad9889c10c798b040d59c92f257cae597a11da372cc3a82931c5e5d6146cd9dd1f">VMA_ALLOCATION_CREATE_MAPPED_BIT</a></div><div class="ttdeci">@ VMA_ALLOCATION_CREATE_MAPPED_BIT</div><div class="ttdoc">Set this flag to use a memory that will be persistently mapped and retrieve pointer to it.</div><div class="ttdef"><b>Definition</b> vk_mem_alloc.h:587</div></div>
<div class="ttc" id="agroup__group__alloc_html_ggad9889c10c798b040d59c92f257cae597add61238d98e20917b9a06c617763f492"><div class="ttname"><a href="group__group__alloc.html#ggad9889c10c798b040d59c92f257cae597add61238d98e20917b9a06c617763f492">VMA_ALLOCATION_CREATE_HOST_ACCESS_RANDOM_BIT</a></div><div class="ttdeci">@ VMA_ALLOCATION_CREATE_HOST_ACCESS_RANDOM_BIT</div><div class="ttdef"><b>Definition</b> vk_mem_alloc.h:648</div></div>
<div class="ttc" id="astruct_vma_allocation_create_info_html_a7fe8d81a1ad10b2a2faacacee5b15d6d"><div class="ttname"><a href="struct_vma_allocation_create_info.html#a7fe8d81a1ad10b2a2faacacee5b15d6d">VmaAllocationCreateInfo::preferredFlags</a></div><div class="ttdeci">VkMemoryPropertyFlags preferredFlags</div><div class="ttdoc">Flags that preferably should be set in a memory type chosen for an allocation.</div><div class="ttdef"><b>Definition</b> vk_mem_alloc.h:1281</div></div>
<div class="ttc" id="astruct_vma_allocation_create_info_html_a9166390303ff42d783305bc31c2b6b90"><div class="ttname"><a href="struct_vma_allocation_create_info.html#a9166390303ff42d783305bc31c2b6b90">VmaAllocationCreateInfo::requiredFlags</a></div><div class="ttdeci">VkMemoryPropertyFlags requiredFlags</div><div class="ttdoc">Flags that must be set in a Memory Type chosen for an allocation.</div><div class="ttdef"><b>Definition</b> vk_mem_alloc.h:1276</div></div>
</div><!-- fragment --><p>A memory type is chosen that has all the required flags and as many preferred flags set as possible.</p>
<p>Value passed in <a class="el" href="struct_vma_allocation_create_info.html#accb8b06b1f677d858cb9af20705fa910" title="Intended usage of memory.">VmaAllocationCreateInfo::usage</a> is internally converted to a set of required and preferred flags, plus some extra "magic" (heuristics).</p>
<h1><a class="anchor" id="choosing_memory_type_explicit_memory_types"></a>
Explicit memory types</h1>
<p>If you inspected memory types available on the physical device and <b>you have a preference for memory types that you want to use</b>, you can fill member <a class="el" href="struct_vma_allocation_create_info.html#a3bf940c0271d85d6ba32a4d820075055" title="Bitmask containing one bit set for every memory type acceptable for this allocation.">VmaAllocationCreateInfo::memoryTypeBits</a>. It is a bit mask, where each bit set means that a memory type with that index is allowed to be used for the allocation. Special value 0, just like <code>UINT32_MAX</code>, means there are no restrictions to memory type index.</p>
<p>Please note that this member is NOT just a memory type index. Still you can use it to choose just one, specific memory type. For example, if you already determined that your buffer should be created in memory type 2, use following code:</p>
<div class="fragment"><div class="line">uint32_t memoryTypeIndex = 2;</div>
<div class="line"> </div>
<div class="line"><a class="code hl_struct" href="struct_vma_allocation_create_info.html">VmaAllocationCreateInfo</a> allocInfo = {};</div>
<div class="line">allocInfo.<a class="code hl_variable" href="struct_vma_allocation_create_info.html#a3bf940c0271d85d6ba32a4d820075055">memoryTypeBits</a> = 1u &lt;&lt; memoryTypeIndex;</div>
<div class="line"> </div>
<div class="line">VkBuffer buffer;</div>
<div class="line"><a class="code hl_struct" href="struct_vma_allocation.html">VmaAllocation</a> allocation;</div>
<div class="line"><a class="code hl_function" href="group__group__alloc.html#gac72ee55598617e8eecca384e746bab51">vmaCreateBuffer</a>(allocator, &amp;bufferInfo, &amp;allocInfo, &amp;buffer, &amp;allocation, <span class="keyword">nullptr</span>);</div>
<div class="ttc" id="astruct_vma_allocation_create_info_html_a3bf940c0271d85d6ba32a4d820075055"><div class="ttname"><a href="struct_vma_allocation_create_info.html#a3bf940c0271d85d6ba32a4d820075055">VmaAllocationCreateInfo::memoryTypeBits</a></div><div class="ttdeci">uint32_t memoryTypeBits</div><div class="ttdoc">Bitmask containing one bit set for every memory type acceptable for this allocation.</div><div class="ttdef"><b>Definition</b> vk_mem_alloc.h:1289</div></div>
</div><!-- fragment --><p>You can also use this parameter to <b>exclude some memory types</b>. If you inspect memory heaps and types available on the current physical device and you determine that for some reason you don't want to use a specific memory type for the allocation, you can enable automatic memory type selection but exclude certain memory type or types by setting all bits of <code>memoryTypeBits</code> to 1 except the ones you choose.</p>
<div class="fragment"><div class="line"><span class="comment">// ...</span></div>
<div class="line">uint32_t excludedMemoryTypeIndex = 2;</div>
<div class="line"><a class="code hl_struct" href="struct_vma_allocation_create_info.html">VmaAllocationCreateInfo</a> allocInfo = {};</div>
<div class="line">allocInfo.<a class="code hl_variable" href="struct_vma_allocation_create_info.html#accb8b06b1f677d858cb9af20705fa910">usage</a> = <a class="code hl_enumvalue" href="group__group__alloc.html#ggaa5846affa1e9da3800e3e78fae2305cca27cde9026a84d34d525777baa41fce6e">VMA_MEMORY_USAGE_AUTO</a>;</div>
<div class="line">allocInfo.<a class="code hl_variable" href="struct_vma_allocation_create_info.html#a3bf940c0271d85d6ba32a4d820075055">memoryTypeBits</a> = ~(1u &lt;&lt; excludedMemoryTypeIndex);</div>
<div class="line"><span class="comment">// ...</span></div>
</div><!-- fragment --><h1><a class="anchor" id="choosing_memory_type_custom_memory_pools"></a>
Custom memory pools</h1>
<p>If you allocate from custom memory pool, all the ways of specifying memory requirements described above are not applicable and the aforementioned members of <a class="el" href="struct_vma_allocation_create_info.html" title="Parameters of new VmaAllocation.">VmaAllocationCreateInfo</a> structure are ignored. Memory type is selected explicitly when creating the pool and then used to make all the allocations from that pool. For further details, see <a class="el" href="custom_memory_pools.html">Custom memory pools</a>.</p>
<h1><a class="anchor" id="choosing_memory_type_dedicated_allocations"></a>
Dedicated allocations</h1>
<p>Memory for allocations is reserved out of larger block of <code>VkDeviceMemory</code> allocated from Vulkan internally. That is the main feature of this whole library. You can still request a separate memory block to be created for an allocation, just like you would do in a trivial solution without using any allocator. In that case, a buffer or image is always bound to that memory at offset 0. This is called a "dedicated allocation". You can explicitly request it by using flag <a class="el" href="group__group__alloc.html#ggad9889c10c798b040d59c92f257cae597a3fc311d855c2ff53f1090ef5c722b38f" title="Set this flag if the allocation should have its own memory block.">VMA_ALLOCATION_CREATE_DEDICATED_MEMORY_BIT</a>. The library can also internally decide to use dedicated allocation in some cases, e.g.:</p>
<ul>
<li>When the size of the allocation is large.</li>
<li>When <a class="el" href="vk_khr_dedicated_allocation.html">VK_KHR_dedicated_allocation</a> extension is enabled and it reports that dedicated allocation is required or recommended for the resource.</li>
<li>When allocation of next big memory block fails due to not enough device memory, but allocation with the exact requested size succeeds. </li>
</ul>
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